After 15 years of political irrelevance, Khan’s Pakistan Tehreek-e-Insaf, or the Movement for Justice Party, is gaining momentum as the ruling coalition fails to improve a slowing economy or fight corruption. Khan’s stance that Pakistan should pull out of a security pact with the U.S. is winning support amid criticism of army offensives against Taliban militants since 2007 that have triggered retaliatory bombings.

“Nobody can stop this tsunami,” Khan, 59, told yesterday’s gathering at the mausoleum of the country’s founder, Muhammad Ali Jinnah, in the port city of Karachi. He vowed to“end corruption and injustice from our society. All I want is your support.” Senior Karachi police officer Javed Odho said 100,000 to 150,000 people attended the event.